With the continuous extension of the scientific research toward the micro field, the technology and products of the micro-manufacturing have developed rapidly in the last decade. The United States, Japan, Germany and other countries have placed micro-manufacturing in a very high position and taken it as one of the mainstream of manufacturing science. Moreover, the development of micro-manufacturing technology and industrial is another area for China to leap toward high technology.
“Deposition Formation” is an important concept in the micro-manufacturing field. The deposition formation can superimpose and accumulate or assemble two-dimensional or three-dimensional micro-structure and component needed “from bottom to top” through the manipulation of micro-particles. The smooth capture, directed transport and precise positioning of the micro-particles are the key technologies and one of the important foundations of “Deposition Formation”. Therefore, how to realize the capture and manipulation of the micro-particles is a research topic hot and difficult in the current field of micro-manufacturing.
According to literature, the capture and manipulation of micro-particles is mainly achieved by means of the laser, the RF pressure and plasma etc until the present time. Optical Tweezers (OT) are the most representative method to achieve the capture and manipulation of the micro-particles. The so-called “Optical Tweezers” is a three-dimensional gradient optical potential wells formed with the use of the mechanical effect of the momentum transfer between light and matter, which is a tool to conduct the non-injury and non-contact manipulation on the micro objects. As early as in 1986, Ashkin of the Bell Labs introduced a single beam laser into a high numerical aperture lens to form a three-dimensional optical potential wells, proving that it could conduct the sub-contact and non-destructive living operations on the catch without affecting the surrounding environment basically and was vividly called “Optical Tweezers”. Since the advent of the “Optical Tweezers”, the research on the “Optical Tweezers” caused by different types of laser beams is more and more comprehensive, and its application is also more and more wide. Until now, from the original single-beam gradient force optical potential well, the “Optical Tweezers” have gradually evolved into the double Optical Tweezers, three Optical Tweezers, four Optical Tweezers, array Optical Tweezers, beam workstation, holographic Optical Tweezers and other different types of optical potential wells, which have provided skillful and effective tools for the research on the micro-manufacturing based on the capture and manipulation of micro-particles.
Secondly, the “Dielectrophoresis” is another way to realize the capture and manipulation of micro-particles. Brown et. al. of the Harvard University used the triaxial atomic force microscope contact-free tweezer (TACT) and the dielectrophoresis to achieve the manipulation of the nano-substances in the aqueous medium. They apply the RF pressure to the needle tip and the inner shell of the TACT and cause the outer shell connected to the ground. The needle tip is designed with opening to let the electric field escape and produce a zero electric field outside the surface. Since the dielectric constant of water is greater than most of the substances, the water will push the nano-particles toward the position of the minimum value of the electric field. As the periphery of the tip belongs to a repulsive force region, it can be ensured that only a particle is captured for one time. This method can be used to capture a single semiconductor quantum, carbon nanotube, semiconductor nanowires, biological particles (e.g. virus) and other micro-particles with the diameter as small as 4 nm, so as to perform the assembly and manipulation of the micro-structure.
In addition, Huang et. al. of the Swiss Federal Institute of Technology, relying on the near-field effect of the plasma, coordinate with the micro-fluidics and the control layer to achieve the capture and manipulation of the micro-particles. They have developed an optofluidic device composed by the plasma optical trap and the micro-fluidics, which can manipulate cells or micro-particles without the complex optical architecture of the traditional “Optical Tweezers”.
The above stated “Optical Tweezers”, “Dielectrophoresis” and “Electromagnetic Field” are three internationally representative ways to achieve the capture and manipulation of the micro-particles at present. However, the realization of the three ways requires the specific hardware equipment; the costs for the construction and using of the whole system are high; moreover, it also has higher requirements on the application environment and is mainly oriented to the research institutes and the personnel researching the theoretical basis in the university and cannot be applied in the industrial practice and conducted the commercialization promotion.